Field Load Test of a Curved Steel I-Girder Bridge During Construction and Comparison with 2D Grid Modeling Approach

Unlike straight bridges with little or no skew, the behavior of curved, steel, I-girder bridges is dependent upon a complex interaction between the girders and cross frames. The ability to accurately predict loads and deformations within the frame system, therefore, requires correctly representing the stiffness of the girders and cross frames. This is particularly challenging when a 2D modeling approach is used, which requires making various assumptions and simplifications that impact behavior. A rare opportunity recently arose during construction of Ramp A5 on the Cleveland Innerbelt Bridge Project in Cleveland, OH, in which the modeling assumptions incorporated in the 2D model used to design the structure were validated through a field load test. The bridge consists of four continuous spans of composite, curved, steel plate I-girders. About two-thirds of the first span is horizontally curved with a radius at roadway baseline of 47.2 m (155.00'). Due to some concerns that arose during construction, a simple load test was performed to verify the behavior of the girder/cross-frame system prior to placement of the slab. A known weight was hung from the girders within the first span and deflections were measured along the girders. The predicted deflections due to the test load from the 2D model were in near exact agreement with those measured in the field. The load test, therefore, validated the assumptions incorporated in the development of the 2D model with respect to girder and cross frame stiffness, and clearly demonstrated the ability to accurately analyze a curved girder system using 2D methods.